Cylinder construction for parallel



Patented Mar. 15, 1949 CYLINDER CONSTRUCTION FOR PARALLEL CYLINDER PUMPS Matthew W. Huber, Watertown, N. Y., assignor to The New York Air Brake Company, a corporation of New Jersey Application November 12, 1947, Serial No. 785,384

4 Claims. (Cl. 103-173) This invention relates to pumps of the variable displacement type, particularly the parallel cylinder type described and claimed in my allowed application Serial No. 626,690,'filed November 5, 1945, now Patent No. 2,433,222 granted December 23, 1947.

In pumps of the type mentioned the cylinders are arranged in circular series around. and parallel with the axis of the drive shaft, and the plungers are actuated by a swash plate fixed on the drive shaft. Displacement is varied by a pressure operated spider which shifts in unison a plurality of valve sleeves which encircle respective plungers and control spill-back ports formed in the valve plungers. In this way the working spaces are connected to the inlet chamber through a greater or less part of each displacement stroke of each plunger, according to the extent to which discharge pressure rises above a desired normal pressure.

To sustain the plungers against the lateral drag of the swash plate, the practice has been to use a guide block, which also sustains the end hearing of the drive shaft. The guide block has thus been a separate part from the cylinder block. While this construction is highly desirable, it is expensive and tends to limit the use of the pump to fields in which cost is a secondary consideration.

The purpose of the present invention is to afford a less expensive construction which will extend the functional advantages of this type of pump into lower price fields.

The fundamental departures from the original design are two. The cylinder block and the guide block are combined in a single casting in which the inlet chamber is cored. For this a high grade iron casting may be used instead of steel. The guide block does not sustain any shaft bearing, all bearings being mounted directly in the pump housing. As a consequence, the swash plate overhangs the bearings. The cylinder for the pressure responsive piston is formed in this unitary casting, and the spider actuated by the piston is of special form and is removably mounted on the piston rod.

A practical embodiment of the inventive concent is illustrated in the accompanying drawing, in which Fig. 1 is an axial section with certain interior parts in elevation.

Fig. 2 is a section through the spill-back valve chamber.

Fig. 3 is a perspective view of the bl ck Showing the mode of assembling spill-back valves and plungers therewith Fig. 4 is a view similar to Fig. 2, but drawn on a slightly smaller scale, and showing a modified construction.

Embodiment of Figs. 1-3

The cylinder block generally indicated by the numeral 6 is itself generally cylindrical in form. It has an internal spill-back chamber 1 to which a central aperture 8 leads through one end, and radial apertures 9 lead through th side. In Fig. 2 there is shown one radial aperture for each pump cylinder, the apertures being centered on the axis of a related pump cylinder. The chamber and the apertures are conveniently formed by coring and their surfaces may be machined to whatever extent is deemed appropriate. I preier to machine all surfaces except the peripheral wall of the chamber and the walls of the radial apertures.

The pump cylinders are simply bores (nine being shown) which are parallel with the axis of the cylindrical block 6, and arranged in circular series around this axis (see Fig. 3). Each bore extends across chamber 1 so that the chamber divides each bore into a pump cylinder portion H and a guideway portion l2..

In each bore is a plunger l3. Each plunger has an axial passage I l' leading from the inner end of the plunger to lateral spill-back ports I5. Each plunger has a flanged head IS with universally tiltable thrust pad II. A coiled compression spring [8 surrounds each plunger. One end is centered in a counterbored seat l9 formed in block 6 and the other reacts against the head flange.

- The spill-back valves are sleeves 2| each slidable on its plunger within chamber 1, and each having a'forked laterally extending lug 22 which straddles the rim of a circular spider disc'23. In block 6 is a guideway coaxial with a slightly larger cylinder bore 24. Reciprocable in the guideway is a stem 25 formed integrally with a piston 26 which works in cylinder 24. Spider disc 23 is releasably fixed on the other end of stem 25 by snap ring 21.

Pump discharge pressure communicated through choke 28 and passage 29 reacts to the right (with reference to Fig. 1) on the annular area of piston 26 outside stem 25 and urges the spill-back valves in a direction to shorten the effective stroke. Inlet flow is through plunger controlled ports 31, one of which is visible in Fig. 1.

Block 6 is clamped between the two halves, a body 32 and cap 33 of the pump housing. It is confined in a close-fitting recess formed partly in the body and partly in the cap and is sealed to the cap by two ring gaskets 34. The cap 33 has an inlet connection 35 which leads to port 3I, and by passage 36 to chamber I. The cap also has a discharge connection 31 which communicates with an annular groove 38 machined in the cap opposite the ends of the pump cylinder bores. Cup-like discharge valves 39 are seated by springs 4| against the end of block 3 and control flow from the cylinder bores to groove 38.

Piston 26 and spider disc 23 are biased to the left by coil compression spring 42. This reacts between spring seat 43 mounted on a nipple formed on the end of piston 26 and a spring seat 44 adjustably supported in cap 33 by a conventional adjusting screw assembly 45 clearly illustrated in Fig. 1.

The body 32 carries two annular ball bearings 46, 41. These are spaced by ring 48 and support the drive shaft 49. Shaft 49 carries the swash plate The shaft is sealed against oil leakage by the oil seal 52. v

The swash plate 5| turns in a chamber 53 which is in communication with chamber 1 and hence with inlet connection 35. There is an overflow connection 54 leading from a channel 55 in chamber 53. A port 56 which enters the swash plate 5| axially and discharges radially induces oil circulation sufllcient to ensure cool- 1 ing and lubrication at all times.

Modification Fig. 4

While it is convenient to have a radial opening 9 opposite each plunger, that is not strictly necessary. When the lugs 22 on the sleeve valves 2I are short enough to clear each other when two adjacent valves are turned (see dotted line position in Fig. 4) there need be a radial opening for only every third plunger.

In Fig. 4 parts corresponding with parts in Fig. 2 are given the same reference numerals increased by 100. Thus the block I06 has three radial openings I09. This ofiers more metal at the periphery for a given diameter.

Assume stem I25 and spider I23 are assembled with block I06. To complete assembly, the three pairs of valves I2I and plungers II3 are inserted as in Fig- 4. They need not then engage spider I23. The lugs I22 can be turned out to clear and thus permit later engagement with spider I23. After this is positioned. the lugs I22 are turned into engagement with it. Finally the remaining three valves I 2I are inserted, after which the last three plungers II3 are inserted.

This particular scheme can be used where the number of plungers is six or some larger multiple of three such as the nine here illustrated. Other variants are possible.

What is claimed is:

1. A cylinder, plunger and spill-back valve assembly for parallel cylinder pumps comprising in combination a block having an axial guideway and a series of pump cylinder bores parallel therewith and surrounding the same in circular series, said block having a central chamber which intersects the bores and divides each into a cylinder portion and a guide portion, a central aperture leading from one end of the block to said central chamber, and a plurality of radial openings extending from the periphery of the block to said chamber; a spider element guided in said guideway and insertible into said chamber through said central aperture; a plurality of spill-back sleeve valves, one for each cylinder,

insertible through said radial apertures and adapted to enter into engagement with said spider; and plungers one inserted into each pump cylinder bore and each extending through a corresponding sleeve valve, said plungers having each a port controlled by the sleeve valve, the parts being so dimensioned as to be held in assembled relation by the plungers and freed for disassembly by the removal of the plungers.

2. A cylinder, plunger and spill-back valve assembly for parallel cylinder pumps, comprising in combination a block having an axial guideway and coaxial regulatory cylinder and a series of pump cylinder bores parallel therewith and surrounding the. same in circular series, said block having a central chamber which intersects the bores and divides each into a cylinder portion and a guide portion, a central aperture leading from one end of the block to said central chamber, and a plurality of radial openings extending from the periphery of the block to said central chamber; a piston and guide insertible into said regulatory cylinder and guideway; a spider insertible into said chamber through said central aperture; means serving to connect said spider and guide; a plurality of spill-back sleeve valves, one for each cylinder, insertible through said radial apertures and adapted to enter into engagement with said spider; and plungers, one inserted into each pump cylinder bore, and each extending through a corresponding sleeve valve.

3. The combination of the structure of claim 2 and a two part housing embracing and confining said block; discharge valves for the pump cylinders, loading means for said regulatory piston and inlet and discharge connections carried by one part of said housing; and plunger-actuating cam means, including drive shaft and bearings carried by the other part of said housing.

i. The combination defined in claim 1 in which the number of cylinders is a multiple of three and not less than six and the radial openings are alined with every third cylinder.

MATTHEW W. HUBER.

No references cited. 

